ANOXIA AND HUMAN PULMONARY VASCULAR RESISTANCE 12

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Abstract
The effect of anoxia induced by the inhalation of 13% O2 in N2 upon the pulmonary arteriolar resistance was studied in human subjects by means of cardiac catheterization. Simultaneous measurements were made of cardiac output and of pulmonary artery, pulmonary "capillary," and brachial artery pressures, before, during and after the period of anoxia. During the anoxia the following changes were observed. There was a rise in the mean pulmonary artery pressure which averaged 24.6%. There was no significant change in pulmonary "capillary" pressure. There was no significant change in cardiac output (direct Fick method). There was a mean increase of 48.5% in pulmonary arteriolar resistance. Where changes were observed they were shown to be statistically significant. Evidence for and against autonomic mediation of this observed anoxic pulmonary vasoconstriction is reviewed. The increase in pulmonary vascular resistance observed to result from anoxia is discussed as to its probable contribution to the pulmonary hypertension of chronic lung disease, mitral stenosis, and left ventricular failure.